ML20084G485

Updated RO 269/83-17:seals at Conduit Connections Defective. Scotchcast 9 Epoxy Resin Will Be Utilized to Seal Conduit Connections,Dow Corning RTV 3145 Applied to Conduit Fittings & Conduit/Cable Seals Will Be Upgraded

ML20084G485
Person / Time
Site:	Oconee
Issue date:	04/18/1984
From:	Tucker H DUKE POWER CO.
To:	James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
References
RO-269-83-17, NUDOCS 8405070243
Download: ML20084G485 (3)

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". April 18, 1984 Mr. James P. O'Reilly, Regional Administrator U. S. Nuclear Regulatory Commission Region II 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30303 Re: Oconee Nuclear Station Docket No. 50-269, -270, -287

Dear Mr. O'Reilly:

.On October 18, 1983 in Duke Power Reportable Occurrence Report R0-269/83-17,. n your office was notified of the potential deficiency of certain seals at conduit connections to safety-related equipment located in harsh environments.

A full environmental qualification test program inclusive of thermal and radiation aging was performed'per the report's Corrective Actions for the chosen moisture intrusion preventative sealant, Dow Corning RTV 3145, to envelope a 40-year qualified life for all Duke Power applications (i.e., Oconee, McGuire, and Catawba Nuclear Stations). Also, the acceptability of the Reactor Building sump monitoring Delaval transmitters as sealed for use in harsh environments at Oconee was reviewed. This correspondence discusses the results of both analyses concerning environmental qualification of connections and updates the corrective actions stated in the original submittal.

After review of the Delaval Qualification. Test Report and Delavall installation requirements, it has been determined that additional modification of the transmitter sealing methods, as recommended in-RO-269/83-17, is not necessary.

(The Delaval transmitters were added for Reactor' Building sump monitoring in response to TM1 concerns.)' The transmitters are filled with Dow 710' silicone fluid'to a level above-the cable-entrance port. The port is sealed-per installa-tion requirements. as was done in the. test, to prevent leakage of the silicone-

' fluid and to provide a seal from the outside. environment. A watertight electrical-

. connection is accomplished by-thel installation of qualified Raychem heat shrink splices in.the terminal box above the transmitters. Due to similarity of' installed and' tested configurations and the seals provided by-the' splices, port sealing, andlthe oil, the~ transmitters as installed are adequately sealed.;

Therefore, the existing cable entrance asealing method used for the Delaval-transmitters used in harsh environments at Oconee is acceptable without additional modifications.

Based on Dow Corning radiation testing for'Dow Corning'RTV 3145 (RTV), Dutre

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Power is confident that the RTV can provide an environmentally qualified short -

term seal.> Dow' Corning data show that RTV 3145 maintains 'its strength and elongation properties with substantial margins'at radiation exposures of approximately 20 megarads, substantially below the. test level of :200 megarads.

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Mr. James-P. O'Reilly, Regional Administrator April 18, 1984 Page'2 ,

This correlates to a qualified life of five years' normal operation with.

approximately four days post LOCA for Duke Power;inside Reactor Building applications. In that Reactor Building spray is terminated at the end of one day post LOCA, and since there is only a short term pressure spike .

(note: the spray and concurrent pressure are the primary forcing functions that contribute to moisture intrusion), it is Duke Power's judgement that ample margin exists in the ability of the RTV to maintain an adequate moisture barrier throughout the primary period of concern for the postulated

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Reactor Building profile. By the time (i.e., approximately four days post LOCA) that the cumulative radiation dose approaches the threshold value ,

to cause RTV degradation, the Reactor Building environment has returned to conditions that should not subject components to significant' moisture intrusion.

With respect to long-term seal qualification of Dow Corning RTV 3145, the Duke Power Company environmental qualification test profiles were very conservative compared to specific application requirements on a station and device basis. Some moisture intrusion was detected during this;all-encompas-sing testing which resulted in the test being inconclusive in regard to the ability of the RTV to provide an acceptable long-term seal for. specific applications. The moisture intrusion'is attributed to the effects of high' radiation (i.e., normal aging plus one year post LOCA dose).

In review of the Dow Corning temperature qualifications for RTV'31'5 4 (i.e.,

qualified to 482*F long-term exposure), Duke Power has determined that the-RTV is fully qualified 1for.outside Reactor Building use. This analysis . ,

consisted of-reviewing the-postulated conditions in.rclation to the physical?

characteristics and limitations of the silicon elastomer-inclusive of'the-results from Duke Power preliminary testing.

Scotchcast 9 epoxy resin,.a sealing method fully qualified for;long-term

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use in harsh environments, is planned to be utilized to seal the conduitJ connections to all affected Unit 3. components. Per the corrective.. action-plan outlined in the October 18, 1983-submittal, Duke Power has. applied' Dow Corning RTV 3145 to the conduit-fittings of all equipment'of concern--

in Oconee Unit 2. Based on the" analysis-provided above and'in the previous

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submittal, Duke Power' finds Dow Corning RTV,3145:to be.an acceptable'short '

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term method of sealing components-locatedfinside the Reactor Building and:

fully qualified forflong-term use outside the Reactor' Building; Duke' Power

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plans to upgrade the-conduit / cable seals'inside 'he Unit 2: Reactor Building -

using Scotchcast 9 epoxy-resin or an alternative fully qualifiedilong-term^

sealing method. Also for Unit 1,--Scotchcast'9 epoxy resin or:an alternative-

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fully ~ qualified long-term sealing method.will be: utilized..

s q The installation schedule for'the modifications, discussed Above'isLas follows:

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l Mr. James P. O'Reilly, Regional Administrator 1 April 18, 1984 l Page 3 l Unit 1 - During the End of Cycle 8 Refueling Outage (estimated to begin November 1984).

Unic 2 - During the End of Cycle 7 Refueling Outage (estimated to begin March 1985).

Unit 3 - During the current End of Cycle 7 Refueling Outage.

This schedule provides sufficient time to prepare and distribute necessary revisions to the installation specification, assemble materials and equipment, and assemble and train installation personnel.

Very truly yours, I

Hal B. Tucker JCP/php cc: Document Control Desk U. S. Nuclear Regulatory Commission Washington, D. C. 20555 1NPO Records Center Suite 1500 1100 circle 75 Parkway Atlanta, Georgia 30339 Mr. J. C. Bryant NRC Resident Inspector Oconee Nuclear Station Ms. Helen Nicolaras Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Washington, D. C. 20555